Enriching chromium(III) from dilute aqueous stream via liquid emulsion membrane process

Abstract

ABSTRACTWastewaters from many industrial processes often contain chromium(III) and chromium(VI) from metallurgical operations is highly toxic. The liquid emulsion membrane (LEM) process performs extraction and stripping simultaneously (eliminating the stripper entirely); this process intensification provides a significant increase in interfacial area for mass transfer. LEM process has been used for the enrichment of Cr(VI), but there is very little published information for the enrichment of Cr(III). In this study, the extraction and enrichment of chromium(III), using di‐2‐ethylhexyl phosphoric acid (D2EHPA) in dodecane was carried out via the LEM process with aqueous methane sulfonic acid (MSA) as the strip phase. The complexation stoichiometric coefficient and equilibrium constant were measured by conventional liquid–liquid extraction studies. Emulsion preparation parameters, such as carrier concentration, surfactant concentration, and internal strip phase (MSA) concentration, were determined in order to obtain the maximum extraction and enrichment. The influence of operating process parameters on the performance of the LEM process, i.e. residence time, speed of agitation and treat ratio (TR), were studied. It was found that 83% extraction and nearly nine times enrichment of chromium(III) was obtained within 6 min of residence time at 400 rpm and 1:10 TR. A simple, but practical, model was developed in order to assist process design studies. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.